The impermissibility of consuming harmful substances not already mentioned explicitly in revealed texts generally derives from the following principles:

General Principle of Avoidance of Harm

The clearest principle is that it is impermissible to consume anything that causes actual material harm to one’s body, whatever that substance may be.

Consuming what Generally Causes Harm

The clearer the harm or its potential, the more readily its impermissibility is established.

Such cases tend to be clear, as the harm, or potential harm, of these substances or foodstuffs causes them to often already be legally regulated. This therefore serves as a useful guideline if one is unsure about the Islamic permissibility of a certain substance.

Harm can also be realized in the form of materials that are not normally considered food, but nevertheless cause harm when ingested.

An example often given in classical texts is the consumption of dirt or soil. Because its consumption is assumed harmful to the body, it is impermissible to do so.

Consuming what Harms a Specific Individual

Impermissibility can also arise for something that is for the majority of the population harmless, or even wholesome.

However, for a specific individual, or a subset of the population, it does cause material harm, perhaps due to an allergy or pre-existing medical condition.

For such individuals, this otherwise permissible foodstuff is impermissible to consume.

Classical texts sometimes posit that if one were to have a materially adverse reaction to honey, it would become impermissible for that person.

Consuming Mind-Altering Substances

Impermissibility can also arise because a substance is mind-altering, such as occurs with the consumption of certain drugs. This is based on what is understood to be the cause for the prohibition of alcohol.

Such substances are impermissible, even if they are shown to not cause material harm to the body. That is, even if they are not legally regulated, they remain impermissible.

Many such substances do in fact materially harm the body, and therefore combine (at least) two reasons for their impermissibility.

Consuming Addictive and Harmful Substances

Some substances are considered impermissible because they materially harm the body, either once or cumulatively, and are addictive.

That is, even if a single usage of such a substance may not cause irreparable immediate harm to the body, the high frequency of addiction or dependency, and concomitant increased usage, will do so.

In such cases, using the substance even minimally may be considered impermissible.

Smoking cigarettes is overwhelmingly considered impermissible because of their immediate and/or long term harm, as well as their addictive nature, which exacerbates its harm.

On the Permissibility of Junk Food

Junk food, as a category, does not fit any of the criterion of harm outlined above for rendering a foodstuff impermissible.

That is, its single or even multiple instances of consumption does not usually cause material harm to a healthy individual.

A person can, for example, drink carbonated drink relatively regularly without it materially harming their body, as the harm is assumed to be negligible.

Neither does the consumption of junk food cause real addiction or dependency to the point of causing such harm.

Using the same example, a person having such a drink will not normally be thought to be at risk of becoming addicted or dependent on it, such that their subsequent increased usage will lead to material harm.

Exceptional Cases of Junk Food Consumption

If, however, a person were to consume an amount of junk food, either once, or over a period of time, such that material harm to their body were to occur because of this, such a course of action would be impermissible.

In the above example, were one to have such a drink multiple times a day over a sufficiently long period of time, thereby materially harming their body, this course of excessive consumption would be impermissible.

Because incremental harm is not readily apparent to the average person, an individual’s actions become blameworthy when they become aware, or should be aware, that their actions are causing material harm to their body.

This can be through common sense – say, drinking, seven such drinks daily for a month – or by being informed of such by a trustworthy or reliable medical practitioner.

God knows best.

Wassalam,
[Shaykh] Shuaib Ally

Shaykh Shuaib Ally is a scholar who has recently returned to Toronto after completing his studies overseas. He started his studies by completing his MA in Islamic Studies at the University of Toronto in 2008. He went on to study in a number of Islamic disciplines privately with scholars in Saudi Arabia, including Tafsir, Qur’anic Sciences, Shafi’i law, Usul, Hadith, Hadith Methodology, Grammar and Balagha. Shaykh Shuaib currently resides in Toronto.